Fish, who earned the No. 1 American ranking thanks to his run this week, hung with Djokovic for a while but went 0 for 6 on break points. Djokovic erased three with aces and another with a service winner.

The Serb’s serve was his biggest weakness only a year ago, but it’s much-improved since. He has yet to be broken in 40 service games at Key Biscayne, erasing all 15 break points he has faced.

Djokovic also is dominating long rallies, another reason he has lost only 18 games in five rounds.

“He’s moving better than anyone right now, no doubt about it, on a hard court,” Fish said. “It’s his playground right now.”

Rain halted the match at 2-all for 54 minutes, and Djokovic said he found conditions less windy and more favorable when play resumed. He stuck out his chest after he won a grueling baseline rally to break for a 4-2 lead.

Fish’s best chance to get back in the match came three games later, but he failed to put away a drive volley on break point and Djokovic served out the set.

It was a runaway from there.

“I didn’t win any of the big points,” Fish said. “None of them. I left a lot of shots out there today. That’s what’s disappointing.”

His consolation: He’ll climb ahead of fellow American Andy Roddick to a career-best 11th in next week’s rankings.

Djokovic finished with only 14 unforced errors and 15 winners, the last coming on match point. He celebrated by pounding his chest with his fist — a familiar scene.

He has won three titles this year, including the Australian Open. His record of 23-0 in 2011 is the best record to begin a year since Ivan Lendl started 25-0 in 1986.

“To be a part of history, it’s always a big pleasure and honor,” Djokovic said.